Walk-behind snowthrowers typically fall into one of two categories. Two-stage snowthrowers include a horizontally-mounted, rigid helical auger that cuts snow and moves it at a low speed transversely toward a discharge area. Once the snow reaches the discharge area, a higher speed impeller collects and ejects the snow outwardly away from the snowthrower through a discharge chute. Wheels supporting two-stage snowthrowers are typically powered to propel the snowthrower over a ground surface during operation.
Conversely, single stage snowthrowers typically achieve both snow collection and ejection using a horizontally mounted, single-stage high-speed rotor. The rotor may be shaped to move the snow transversely toward a discharge area. At or near the discharge area, the rotor may include paddles configured to directly eject the snow outwardly through a discharge chute.
Typically, the rotor of a single-stage snowthrower is constructed of an elastomeric material. Thus, unlike the auger of a two-stage unit, the rotor may be configured to contact the ground surface during operation. Such contact may assist in propelling the single-stage snowthrower, negating the need for powered propulsion wheels. Passive wheels may still be provided to support the snowthrower in rolling engagement with the ground surface.